Simulation of expected future efficacy from HRAC group B herbicides against loose silky-bent grass, depending on cropping factors

Abstract

Results from the resistance monitoring on loose silky-bent grass conducted in 2014 in Hessen showed that resistance against herbicides from HRAC group B is disseminated throughout the federal state. Cropping data like seeding date, ploughing intensity etc. where collected for fields involved in the monitoring in order to identify the impact of such cropping practices on herbicide efficacy and evolution of resistance. Correlations were calculated between field cropping data and corresponding efficacy rates against loose silky-bent grass, generated from bioassays conducted in 2014. A simulation model was developed and validated to forecast efficacy rates in dependence of the collected cropping data. The simulation results demonstrate high efficacy losses if the proportion of herbicide from the HRAC group B will increase in the crop rotation. To neutralize the effect, ploughing intensity would have to increase and proportion of winter cereals should decrease. The simulation model should be applied to further datasets and further trained, to forward anti-resistance strategies.